1. Field
The present invention relates generally to data packet transmission and specifically to the use of micro-tunnels.
2. Background
Internet Protocol (IP) “tunnels” have become a widespread mechanism to transport data units, referred to as datagrams, over the Internet. Using Tunneling involves incorporating an original IP packet inside of another IP packet. Tunneling also has additional connotations about changing the effects of Internet routing on the original IP packet.
Typically, a tunnel is used to augment and modify the behavior of the deployed routing architecture, such as in multicast routing, mobile IP, and Virtual Private Network (VPN). From the perspective of traditional best-effort IP packet delivery, a tunnel behaves as any other link. Packets enter one end of the tunnel, and are delivered to the other end unless resource overload or error causes them to be lost.
Information may be encapsulated and routed through a tunnel. In the most general case, a system has a packet, which is referred to as a payload packet, which needs to be encapsulated and routed. The payload packet is first encapsulated in a Generic Routing Encapsulation (GRE) packet, which possibly also includes a routing. The resulting GRE packet may then be encapsulated in some other protocol and then forwarded. This outer protocol is referred to as the delivery protocol.
For mobile IP, a wireless system interfaces with an IP network. Tunnels are used for transporting data from the IP network to infrastructure elements in the wireless system. The data may involve multiple streams of data for transmission to and/or from a same mobile node. In this case, the system must establish individual tunnels for each stream.
In mobile IP the home agent associated with the mobile node redirects packets from the home network to the care-of address by constructing a new IP header containing the mobile node's care-of address as the destination IP address. The home agent is a router on a mobile node's home network maintaining information about the device's current location, as identified in its care-of address. The care-of address is a temporary IP address for a mobile node enabling message delivery when the device is connecting from somewhere other than its home network. The care-of address identifies a mobile node's current point of attachment to the Internet and makes it possible to connect from a different location without changing the device's home address (permanent IP address). The new header then shields or encapsulates the original packet, causing the mobile node's home address to have no effect on the encapsulated packet's routing until it arrives at the care-of address. Such encapsulation is also called tunneling, which suggests the packet burrows through the Internet, bypassing the usual effects of IP routing.
In a mobile IP environment, there is a need to identify multiple tunnels each associated with a same mobile node. Further, there is a need for flexible tunnel set up which optimizes the resources of the system.